1. Field of the Invention
This invention relates to a track ball coordinates data inputting device which is employed as an external input device for personal computers, word processors or the like, to simplify an operation of inputting and specifying data on X-Y coordinate positions with high accuracy.
2. Related Art
A conventional track ball coordinate data inputting device of this type (hereinafter referred to as "a track ball device", when applicable) is designed as shown in FIGS. 5 through 7. The track ball device 1 comprises: a casing 2; a coordinates inputting ball 3 which partially appears in the upper surface of the casing 2; a pair of drivers 4 and 5 provided inside the casing 2 in such a manner that they are in contact with the ball 3 in two directions which are perpendicular to each other; and two detecting sections 6 and 7 adapted to detect an amount of rotation of the ball 3 as X-coordinate data and Y-coordinate data.
The detecting sections 6 and 7 are connected to a printed circuit board (not shown) having a predetermined conductor pattern which is provided inside the casing 2. In addition, for instance coordinate position determining and nullifying micro-switches are mounted on the printed circuit board which are operated with push buttons provided on the upper lid of the casing 2.
The ball 3 is accommodated in an accommodating section 8a circular in section, which is provided at the center of a synthetic resin frame member 8 in such a manner that it is opened upwardly. In order to rotatably support the ball 3 in such a manner that it floats in the accommodating section 8a, a plurality of supporting ball elements 9 (five supporting ball elements in the case of FIG. 6) are rotatably held with their outer surfaces partially exposed inwardly of the spherical inner wall of the accommodating section 8a.
That is, the ball 3 is not in contact with the spherical inner wall of the accommodating section 8a, and instead it is in point contact with the supporting ball elements 9. Hence, the ball 3 can be smoothly turned with a considerably small operating force.
With the track ball device 1, the direction of rotation and the amount of rotation of the ball 3 are detected by the detecting sections 6 and 7 with the aid of the drivers 4 and 5. The output detection signals of those detecting sections 6 and 7 are applied through connecting cables to a computer or the like, so that the cursor is moved on the screen of a display unit connected to the computer. In this operation, the position of the cursor at that time is determined or nullified by operating the input button on the casing 2.
In the conventional track ball device 1 designed as described above, the supporting ball elements 9 are put in five recesses 8b, respectively, which are formed at equal angular intervals in the inner wall of the accommodating section 8a of the frame member 8, and a ring-shaped holding member 8c is placed over the supporting ball elements 9, so that the latter 9 are held in the recesses 8b under pressure. Under this condition, legs 8d extended from the ring-shaped holding member 8c are inserted into through-holes 8e, respectively, which are formed adjacent to the recesses 8b, until the end portions of the legs 8d are protruded from the lower ends of the through-holes 8e. The end portions thus protruded are peened, so that the ring-shaped holding member 8c is fixedly secured to the frame member 8. Hence, it is rather intricate and troublesome to assemble the components for holding the supporting ball elements 9. In addition, the assembling work cannot be achieved without the skilled person. As a result, the resultant track ball device is liable to be high in manufacturing cost, and low in assembling accuracy.